可能误以为空语句警告

Question

我得到一个“可能错误的空语句”的警告，当我编译此代码：

class Lab6 
{ 
    static void Main(string[] args) 
    { 
     Program fileOperation = new Program(); 

     Console.WriteLine("Enter a name for the file:"); 
     string fileName = Console.ReadLine(); 

     if (File.Exists(fileName)) 
     { 
      Console.WriteLine("The file name exists. Do you want to continue appendng ? (Y/N)"); 
      string persmission = Console.ReadLine(); 

      if (persmission.Equals("Y") || persmission.Equals("y")) 
      { 
       fileOperation.appendFile(fileName); 
      } 
     } 
     else 
     { 

      using (StreamWriter sw = new StreamWriter(fileName)) ; 
      fileOperation.appendFile(fileName); 
     } 
    } 

    public void appendFile(String fileName) 
    { 
     Console.WriteLine("Please enter new content for the file - type Done and press enter to finish editing:"); 
     string newContent = Console.ReadLine(); 
     while (newContent != "Done") 
     { 
      File.AppendAllText(fileName, (newContent + Environment.NewLine)); 
      newContent = Console.ReadLine(); 
     } 
    } 
} 

我试图修复它，但我不能。这个警告是什么意思，问题在哪里？

Answer 1

“可能是空的错误语句”警告意味着代码中有一个声明，应该是复合的（即包含一个“body”，例如：statement { ... more statement ... }），但是代替body的是分号;，它会终止声明。您应该立即知道哪里和哪里出了问题，只需双击导航到相应代码行的警告即可。

像这样常见的错误是这样的：

if (some condition) ; // mistakenly terminated 
    do_something(); // this is always executed 

if (some condition); // mistakenly terminated 
{ 
    // this is always executed 
    ... statement supposed to be the 'then' part, but in fact not ... 
} 

using (mySuperLock.AcquiredWriterLock()); // mistakenly terminated 
{ 
    ... no, no, no, this not going to be executed under a lock ... 
} 

具体来说，在你的代码在此声明：

using (StreamWriter sw = new StreamWriter(fileName)) ; 

有一个;底，使得using空（=没用）。紧随其后的代码行：

fileOperation.appendFile(fileName); 

无关任何StreamWriter任何，所以有明显东西代码中的缺失（或东西遗留 - 在using，大概？）。